Monoclonal antibody technology allows the specificity of an antibody for its antigen to be used in targeting cancer cells. Bifunctional chelating agents are compounds with a strong metal chelating group at one end and a reactive functional group capable of binding to proteins at the other. When conjugated to monoclonal antibodies, these agents act as carriers of radiometals for tumor targeting. Over the past several years, we have created a number of new laboratory methods to prepare and characterize metal chelates for medical use. Mass spectrometry has much to offer in augmenting our methods to provide mass analysis of chelating agents and related compounds.